1. Field of the Invention
An apparatus for continuously driving long, flexible or deformable products in order to give them a curvature and especially to make them assume a helical form, with a view to subjecting them to a treatment chamber.
2. Description of the prior art
In order to subject a long product of small section, such as a wire, tube or strip, to a cleaning treatment, a chemical treatment or electrolytic treatment, etc..., it is known to bring this long product into helical form at the inlet end of a chamber in which the treatment is carried out, and to cause it to progress in said chamber by rotation of the helix on itself, this latter being supported by one or more bearing shafts. This method of causing a considerable reduction in the size of the treatment zone ensures that the treatment proceeds with excellent regularity and permits an increase in the speed in the chamber and hence in the output of the treated long product.
Several apparatus exist which permit a product of great length to be brought into helical form. Thus, it is known to use a bending or stamping press, of which the punch and the die have a groove with the desired curvature and a section complementary with that of the long product to be brought to helical form. The press operates intermittently and permits a regularity in curvature to be obtained. On the other hand, the use of such a press presents very many inconveniences; costly tooling, specific to the section of the long product to be formed into a helix; the necessity of greasing the punch and die so as to avoid premature wear, with which there is a risk of causing binding of the product, delicate joining of two lengths of long product, because of the thickness of the joining or butting zone: functioning of the press in fits and starts, and therefore slowly, this making it necessary for the arrangement receiving the helix also to function intermittently; irreversibility of the method, thereby preventing a broken joint to be returned to the front end, where it could be conveniently remade.
It is also known to use a capstan having a smooth drum. The rotation of the capstan on its shaft causes the formation of a succession of turns, the diameter of which is equal to that of the drum. However, in order to avoid the turns overlapping one another, it is essential to impose a first displacement of the capstan along its axis relatively to the initial supply drum and then a rearward return movement at the moment when the last turn being formed is made in the immediate vicinity of the rear face or edge of the drum. The use of a smooth drum capstan therefore involves a complex and heavy installation, and also has the disadvantage that it is irreversible.
It is also known to use a rolling mill having grooved rollers or pulleys, particularly in connection with wire, the functions of driving and bending being respectively assured by different coupled rollers and by one or more rollers, which may or may not be coupled. This apparatus permits a wire of any sectional form to be driven without any danger of deformation, on condition that the coupled rollers or pulleys which ensure the driving action are provided with a groove matching the sectional form. Nevertheless, the driving force is relatively weak, since the contact between wire and roller is only punctiform for each generatrix of the wire, and because the pressure exerted on this wire by coupled driving rollers has to be moderated so as not to crush or flatten it, which could have the disadvantage of altering the shape of its section, so as not to hammer-harden it (unless this should be desirable) and finally so as not to disturb the regularity of the expected bending effect.
An apparatus which functions on the same principle as the roller-type rolling mill is the cylinder-type rolling mill for flat strips. This apparatus permits a strip of any section to be driven, always provided that the table of the cylinder is sufficiently large. It does not present the disadvantage of hammer-hardening as previously mentioned in respect of the groove-type rolling mill. On the other hand, only flat strips or plates can be correctly driven by the cylinder-type rolling mill; such a mill is incapable of driving profiled strips.
A self-locking capstan is also known which acts by one length of wire being pinched by another in a groove, the wire passing over a satellite between its two successive passes in the groove. An apparatus of this type is described in French Pat. No. 1,353,965. Such a capstan gives a wire a practically constant radius of curvature and its tractive force is considerable; it would be sufficient for the wire to be drawn through a wire-drawing die. On the other hand, the following disadvantages are found; only the wires having a round section can be driven, the self-locking capstan being incapable of operating with wires having a square, rectangular, hexagonal or any other section; the self-locking capstan is not reversible and rearward movement is impossible; during the passage of the wire from the capstan to the satellite and then from the satellite to the capstan there is considerable danger of causing cold-rolling of the wire; and gripping and then the loosening of the wire in the groove provides the risk of causing scoring of the surface. Further it is not easy for the wire to be introduced, it being necessary for the first few meters of a ring of wire to be positioned by hand. For this reason, it is necessary to stop the capstan each time a new wire has to be introduced, and at least to solder it end to end with the preceding wire. Furthermore, each time it may be a question of introducing into the installation a new wire which is impossible to join up with the preceding wire, either because of their common nature, or because of their differences as regards nature or section, so that the first few meters of this new wire are engaged manually, first of all on the capstan, then on the satellite, and finally once again on the capstan, without it being possible for them to be brought under regular conditions as regards tension, from which the following meters would benefit. The result is that these first meters leave the capstan with inevitable malformations, so that it is necessary for them to be removed and discarded.
All the apparatus as described above are able to receive long products which are of round or flat sectional form. However, they cannot accept the section members, particularly having a section in the form of a closed curve, some parts of which are concave and some convex. This is their main disadvantage.